Sampling Bias

Sampling Bias refers to errors that can occur in research studies by not properly selecting participants for the study. Study participants should be chosen completely randomly within the criteria of the study but without factors that might influence the results. It risks the internal validity of a study if any bias exists in the choosing of participants. Example: In an arthritis study the subjects might need to fall within criteria of age, gender, and type of arthritis, but the study might need to exclude individuals with other health problems that might interfere with the proposed treatment.